Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i
This work is the second part of the set of measurements of v sin i forA-type stars, begun by Royer et al. (\cite{Ror_02a}). Spectra of 249 B8to F2-type stars brighter than V=7 have been collected at Observatoirede Haute-Provence (OHP). Fourier transforms of several line profiles inthe range 4200-4600 Å are used to derive v sin i from thefrequency of the first zero. Statistical analysis of the sampleindicates that measurement error mainly depends on v sin i and thisrelative error of the rotational velocity is found to be about 5% onaverage. The systematic shift with respect to standard values fromSlettebak et al. (\cite{Slk_75}), previously found in the first paper,is here confirmed. Comparisons with data from the literature agree withour findings: v sin i values from Slettebak et al. are underestimatedand the relation between both scales follows a linear law ensuremath vsin inew = 1.03 v sin iold+7.7. Finally, thesedata are combined with those from the previous paper (Royer et al.\cite{Ror_02a}), together with the catalogue of Abt & Morrell(\cite{AbtMol95}). The resulting sample includes some 2150 stars withhomogenized rotational velocities. Based on observations made atObservatoire de Haute Provence (CNRS), France. Tables \ref{results} and\ref{merging} are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.125.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/393/897
|
A-shell stars in the Geneva system
Among the various kinds of A stars having a peculiar spectrum, we findthe A-shell stars. Many questions are still open concerning these stars,including their evolutionary status. In the present study we have useddata from the Hipparcos catalogue to examine this point. We have foundthat the majority of A-shell stars are well above the main sequence. Nodifferences could be established between A-shell stars in luminosityclasses III and I and those in luminosity class V as regardsvariability, duplicity, or the importance of the shell feature.
|
Catalogue of H-alpha emission stars in the Northern Milky Way
The ``Catalogue of Stars in the Northern Milky Way Having H-alpha inEmission" appears in Abhandlungen aus der Hamburger Sternwarte, Band XIin the year 1997. It contains 4174 stars, range {32degr <= l() II< 214degr , -10degr < b() II < +10degr } having the Hαline in emission. HBH stars and stars of further 99 lists taken from theliterature till the end of 1994 were included in the catalogue. We givethe cross-identification of stars from all lists used. The catalogue isalso available in the Centre de Données, Strasbourg ftp130.79.128.5 or http://cdsweb.u-strasbg.fr and at the HamburgObservatory via internet.
|
Beta Pic-like circumstellar disk gas surrounding HR 10 and HD 85905
We present high spectral resolution observations of the absorption linesof Ca II and Na I associated with the circumstellar gas disk surroundingthe two A-type shell stars HR 10 and HD85905. Data taken over two four-night periods in January andNovember 1997 reveal substantial changes in the circumstellar absorptionline profiles between successive observations of both stars. Suchvariable features have both blue and red-shifted velocities up to 50 kms(-1) away from the central absorbing component, and are similar tothose routinely observed in the beta Pictoris system. The sporadicpresence of the circumstellar absorption components observed towardsboth HR 10 and HD 85905 may be explained by the infalling evaporatingcomet model developed for the beta Pictoris system by Beust {et al./}(\cite{beust90}). We note that variable circumstellar absorptionfeatures have also been detected in rapidly rotating A-type stars, suchthat they may be suffering irregular mass-loss that could give rise tosimilar circumstellar disks and shells.
|
Catalogue of stars in the northern Milky Way having H-alpha in emission
Not Available
|
Photovisual Magnitude Differences for 169 Double Stars
Photovisual magnitude differences determined from multi-exposurephotographic plates for 169 double stars are presented. The separationsrange from 1.5'' to 113\arcsec, and the photovisual magnitudedifferences vary from 0.03 to 6.14 magnitudes. The internal mean errorof a single magnitude difference estimate is +/-0.064 magnitude.
|
The beta Pictoris Phenomenon in A-Shell Stars: Detection of Accreting Gas
We present the results of an expanded survey of A-shell stars using IUEhigh-dispersion spectra and find accreting, circumstellar gas in theline of sight to nine stars, in addition to the previously identifiedbeta Pic, HR 10, and 131 Tau, which can be followed to between +70 and100 km s-1 relative to the star. Two of the program stars, HD 88195 andHD 148283, show variable high-velocity gas. Given the small number ofIUE spectra for our program stars, detection of high-velocity, accretinggas in 2/3 of the A-shell stars sampled indicates that accretion is anintrinsic part of the A-shell phenomenon and that beta Pic is not uniqueamong main-sequence A stars in exhibiting such activity. Our programstars, as a group, have smaller column densities of high-velocity gasand smaller near-IR excesses compared with beta Pic. These features areconsistent with greater central clearing of a remnant debris disk,compared with beta Pic, and suggest that the majority of field A-shellstars are older than beta Pic.
|
The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJS...99..135A&db_key=AST
|
Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
|
Radial velocity studies of A-type shell stars.
We have measured radial velocities for a sample of A-type shell stars.We examine the results for the H I, Ti II and Ca II shell lines andcompared them with the radial velocities derived for the underlyingstars. We found that the A-type shell stars reproduce on a smaller scalethe phenomena observed in B-type shell stars.
|
The beta Pictoris Phenomenon in A-Shell Stars
We present the results of an on-going survey of IUE recent and archivalspectra of A-shell stars for accreting, circumstellar gas similar tothat seen toward beta Pic. Compared to previous, optical surveys, theUV, and particularly the mid-UV is rich in high-oscillator strengthtransitions of cosmically abundant elements, providing more sensitiveprobes of circumstellar material than can be obtained in opticalsurveys. Accreting material is detected in HD 88195, HD 38090, HD 15253,HD 38090, and HD 42111 in addition to the previously reported detectionsfor HR 10, 51 Oph, and beta Pic. Given the limited number of IUEobservations, together with the high detection rate, the available dataimply that accreting circumstellar gas is routinely in the line of sightto these stars, in contrast to the classical Be stars for whichaccretion events are comparatively rare. The optically brighter stars inour sample are IRAS sources; given the faint V magnitudes we havedetected either the presence of companions or circumstellar dust.Several of the program stars have residual Hα emission in publishedspectra. Previous studies have suggested that A-shell stars represent anextension to lower stellar luminosities of the classical Be phenomenon,in which case we would expect only sporadic detections of accretingmaterial. Nevertheless, the overall level of the accreting gas, thepresence of incipient Hα emission, and the presence of modest IRexcesses, compared to Herbig Ae stars, suggests a closer link to theHerbig Ae stars and objects like beta Pic. This study was supportedunder NASA Contract NASW-4756 to the Applied Research Corporation.
|
A preliminary compilation of DS-programme star positions
A catalog is presented of the double-star-program (DS-program) starpositions, listing right ascensions for 930 DSs and declinations for1225 DSs of the program. The positions were compiled from the observedvalues obtained between 1980 and 1987 with the meridian circles of sixUSSR observatories (the Moscow, Kazan', Kiev, Khar'kov, Odessa, andTashkent Observatories) and the Belgrade Observatory. The measurementsand the treatment of the observational material were performed using therelative method, and the FK-4 system stars were used as reference stars.
|
Anomalous infrared emitters among A-type stars
Spectroscopic observations of a sample of 26 stars have been analyzed inthe blue and near-IR to find out if anomalous IR emitters (AIEs) have aspectral signature. It is found that many, but not all, such starsexhibit shell characteristics. Analysis of available IRAS photometricobservations of A-type stars shows that the detection of circumstellarfeatures depends strongly on the number of IR bands at which the objectwas observed. Out of the 707 stars observed by IRAS, 41 AIEs, or 5.7percent, are found. Among nonsupergiant AIEs, 23 percent show shellfeatures. The true percentage of AIEs among A-type stars is estimated tobe 1.5 percent in a volume-corrected sample. A list of 24 stars whichwere apparently not previously detected as AIEs is given.
|
AE and A-type shell stars in the near infrared
Spectroscopic observations in the near-infrared of a number of Ae and Ashell stars are presented. It is shown that shells can be detectedthrough the enhancement of the lambda 7773 line and through otherspectroscopic criteria.
|
Search for Beta Pictoris-like star
The results are reported of a systematic search for Beta Pic-like stars,undertaken at ESO, CFHT and OHP. The candidate stars, either IRAS excessstars or shell stars, are investigated by means of high resolutionspectroscopy in the Ca II and Na I lines, which in the case of Beta Pic,are very peculiar. The observations are presented and it is shown thatamong the selected stars, few do show spectral similarities with BetaPic. Some interesting cases, HR10, HR2174, HR9043 and HR6519 arediscussed.
|
The Paschen P7 line in Be, AE and shell type stars
Observations of 36 Be, Ae, and shell stars in the region 984-1020 nm arepresented. P7 is seen in emission until AO and not afterwards. Fe II999.7 nm is seen in emission in about the same types; both emissionshave similar structures, and a good correlation exists between theequivalent widths of both lines. Also detected in nine Be stars is1.0173-micron emission and in four stars 995.6-nm emission. Both linesbelong to Fe II and appear when 999.7 nm is strong in emission.
|
2000 A UV imaging of a 6 deg diameter field around the H and Chi Persei double cluster
A stellar field centered close to the h and Chi per double cluster hasbeen observed at 2000 A by the stratospheric balloon-born telescope ofthe SCAP-2000 program. It is shown that the prevailing extinction lawproduces greater extinction at 1965 A than is predicted by the meanextinction law. The results suggest the presence of an H2 cloud in frontof h and Chi Per in the second absorbing layer and in the local arm. Agroup of hot stars centered at the same distance as the molecular cloudmay form an association of OB stars in the local arm.
|
A survey of AE and A-type shell stars in the photographic region
A total of 28 northern Ae and A-type shell stars were observed in thephotographic spectral region. A regular pattern of line behavior withspectral type was found, which in part prolongs the behavior of Be starstoward cooler stars, although a discontinuity seems present around A0. Asurvey of other data concerning colors, rotation, variability, etc., isalso presented. Photometrically the stars simulate the behavior ofhigher-luminosity objects. A large proportion of shells seems to bevariable. The attempt to detect new shell stars among 13 stars known tobe rapid rotators with normal spectra failed, however.
|
The H-alpha line in AE and A shell stars
The H-alpha profiles of a sample of 20 Ae and A shell stars areanalyzed. In the earlier types, emission features are present; in themiddle A-types only absorption cores are seen; and in the late A-typesthe H-alpha profiles are normal both in the profiles and the equivalentwidths. In this latter group the shell features visible in the360-480-nm region are unrelated to H-alpha. Because of the short timeinterval covered, some few cases of variability are found.
|
Photometric variability of B- and A-type supergiants
Photometric observations of 16 early-type (O9 to A3) supergiants havebeen obtained. All but two of the stars are variable, with a range ofabout 0.05 mag. The light curves are irregular, but characteristic timescales or 'quasi-periods' can be identified. The ratio of thequasi-period to the theoretical period (for pulsation in the fundamentalradial mode) varies from 2-10 in the earliest-type supergiants to 0.2-2in the later-type supergiants. The variability is most likely due tononradial pulsation, at least in the O-B-type supergiants.
|
Photographic Measures of Visual Double Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1983A&AS...51...63P&db_key=AST
|
Photographic Measures of Double Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&AS...41..319P&db_key=AST
|
Wavelength dependence of polarization. XXXIII - The Alpha Persei star cluster
This paper presents multicolor polarization observations of a largenumber of stars that are highly probable members of the Alpha Perseistar cluster and of certain surrounding stars in order to determine thewavelength dependence of polarization due to dust grains in andsurrounding the cluster. It is concluded that the grains in the clusterare no different from those in the general interstellar medium. The dataare combined with previously published work in order to determinepolarization-to-absorption ratios and to make better estimates of thedistance, size, and mass of the cluster and its associated gas and dustcloud. From these parameters it is concluded that a magnetic field ofabout 100 microgauss is necessary to produce the observed polarization.The role of the magnetic field in the cluster's evolution is discussed.
|
Near infrared magnitudes of 248 early-type emission-line stars and related objects.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973MNRAS.161..145A&db_key=AST
|
Further Bright Peculiar A Stars
Not Available
|
The Changing Spectra of Four Shell Stars
Not Available
|
Polarimetric Observations of Nearby Stars in the Directions of the Galactic Poles and the Galactic Plane
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968ApJ...151..907A&db_key=AST
|
MK Spectral Types for 185 Bright Stars
Not Available
|
